Disclosure of Invention
In view of the above, the embodiment of the invention provides a wide-dynamic-range wide-frequency alternating-current and direct-current magneto-sensor with milliamp-level to hundred-amp-level, which solves the technical problem that the chip is saturated and weak current measurement cannot be performed due to power frequency load current when the wide-frequency circuit measurement is performed by adopting a tunneling magneto-resistance technology in the prior art.
The technical scheme provided by the embodiment of the invention is as follows:
The first aspect of the embodiment of the invention provides a wide-frequency alternating-current/direct-current magnetic sensor with a large dynamic range from milliampere level to hundred ampere level, which comprises a first induction circuit, a second induction circuit, a power frequency current conditioning circuit and a weak current conditioning circuit, wherein the first induction circuit and the second induction circuit are respectively connected with the power frequency current conditioning circuit, the second induction circuit is connected with the weak current conditioning circuit, the first induction circuit and the power frequency current conditioning circuit adopt a tunneling reluctance technology and a magnetic balance principle to induce a wide-frequency mixed current to be detected and extract the power frequency current in the wide-frequency mixed current to be detected, the second induction circuit adopts the magnetic balance principle to induce the wide-frequency mixed current to be detected, the power frequency feedback current is received to offset the power frequency part in the wide-frequency mixed current to be detected, the weak current conditioning circuit adopts the tunneling reluctance technology to sense the weak current remained after the power frequency part is offset, and the weak current conditioning circuit performs weak current measurement.
Optionally, the first induction circuit comprises a first magnetic core provided with an air gap, a first feedback coil and a high-saturation magnetic resistance chip, wherein the first feedback coil is wound on the first magnetic core, the high-saturation magnetic resistance chip is arranged in the air gap, and the high-saturation magnetic resistance chip induces broadband mixed current to be detected by adopting a tunneling magnetic resistance technology.
Optionally, the second induction circuit comprises a second magnetic core provided with an air gap, a second feedback coil and a high-sensitivity magnetic resistance chip, wherein the second feedback coil is wound on the first magnetic core, the high-sensitivity magnetic resistance chip is arranged in the air gap, and the high-sensitivity magnetic resistance chip adopts a tunneling magnetic resistance technology to induct weak current remained after the power frequency part is counteracted.
The power frequency current conditioning circuit comprises a compensation circuit, a sampling resistor, a current mirror circuit and a band-pass filter, wherein one end of the compensation circuit is connected with the high-saturation magnetic resistance chip, the other end of the compensation circuit is connected with one end of the first feedback coil, the other end of the first feedback coil is connected with one end of the current mirror circuit through the sampling resistor, the compensation circuit is used for recording broadband mixed current to be detected, which is induced by the high-saturation magnetic resistance chip, the other end of the current mirror circuit is connected with one end of the band-pass filter, the other end of the band-pass filter is connected with the second feedback coil, the current mirror circuit is used for copying and outputting the broadband mixed current to be detected, which is recorded by the compensation circuit, and the band-pass filter is used for extracting the power frequency current in the broadband mixed current to be detected, which is output by the current mirror circuit, so as to obtain the power frequency feedback current, and inputting the power frequency feedback current to the second feedback coil.
Optionally, the compensation circuit comprises an amplifying circuit, an integrating circuit, a filtering circuit and a push-pull output circuit which are sequentially connected.
Optionally, the current mirror circuit comprises a first resistor, a first triode and a second triode, wherein one end of the first resistor is connected with the other end of the compensation circuit, the other end of the first resistor is connected with a collector electrode and a base electrode of the first triode and a base electrode of the second triode, an emitter electrode of the first triode is connected with an emitter electrode of the second triode and is grounded, and a collector electrode of the second triode is connected with one end of the band-pass filter.
Optionally, the band-pass filter includes first electric capacity, second electric capacity and second resistance, the one end of first electric capacity is connected the other end of current mirror circuit and the one end of second resistance, the other end of second resistance is connected the one end of second electric capacity, the other end of first electric capacity is connected the other end of second electric capacity and ground connection.
Optionally, the weak current conditioning circuit comprises an amplifying filter circuit and a trap.
Optionally, the milliamp-level to hundred-amp-level wide dynamic range broadband alternating current-direct current magneto-dependent sensor further comprises a power supply, wherein the power supply is used for supplying power to the first induction circuit, the second induction circuit, the power frequency current conditioning circuit and the weak current conditioning circuit.
Optionally, the power supply is powered by adopting a mode of externally inputting electric energy, photovoltaic energy storage or magnetic field energy taking.
The technical scheme of the invention has the following advantages:
The wide-frequency alternating-current and direct-current magnetic sensor with the wide dynamic range from the milliampere level to the hundred ampere level provided by the embodiment of the invention adopts the tunneling magnetic resistance technology to induce the wide-frequency mixed current to be measured, fully exerts the advantages of high sensitivity, low power consumption, simple structure, non-invasiveness and the like of the tunneling magnetic resistance current measurement technology, simultaneously adopts the magnetic balance principle to realize the measurement of the wide-frequency mixed current to be measured and the extraction of the power frequency current by combining the first induction circuit with the power frequency current conditioning circuit, inputs the obtained power frequency feedback current into the second induction circuit, and partially counteracts the power frequency in the wide-frequency mixed current to be measured induced by the second induction circuit, thereby avoiding the problem that the second induction circuit is saturated and cannot perform weak current measurement due to the fact that the power frequency current is large.
The milliamp-level to hundred-amp-level wide-dynamic-range broadband alternating current-direct current magneto-dependent sensor provided by the embodiment of the invention is provided with the high-saturation magneto-resistance chip and the high-sensitivity magneto-resistance chip, wherein the high-saturation magneto-resistance chip is used for measuring the power frequency current with large amplitude, and meanwhile, the power frequency current is injected into the second feedback coil to counteract the induction magnetic field generated by the power frequency current with large amplitude, so that the saturation of the high-sensitivity tunneling magneto-resistance chip is avoided. Therefore, the high-sensitivity tunneling magneto-resistance chip can work normally, can measure weak direct current, harmonic and inter-harmonic components superposed on large-amplitude power frequency current, and can be applied to the scenes such as high-precision harmonic and direct current magnetic bias current monitoring of a distributed power supply access scene, line single-phase grounding fault searching based on a high-frequency injection method and the like.
Detailed Description
As described in the background art, the technologies of the conventional current transformer, the optical fiber current transformer and the like are limited by sensitivity, volume, installation mode and the like, and weak current measurement is difficult to realize. In recent years, tunneling magneto-resistance technology has received extensive attention due to its advantages of high sensitivity, adjustable magnetic saturation range, small volume, non-invasiveness, and the like. When the tunneling magneto-resistance technology is adopted to measure the broadband current in the related technology, the measuring range of the sensor can be improved by combining a closed-loop sensor based on a high-sensitivity tunneling magneto-resistance sensing chip and an open-loop sensor based on a low-sensitivity sensing chip.
However, this technique is not suitable for wide-dynamic-range broadband mixed current measurement, because the power frequency load current is generally large, which causes saturation of the high-sensitivity sensor chip, and weak direct current, harmonic and inter-harmonic components cannot be measured.
In view of the above, the embodiment of the invention provides a wide-frequency alternating-current/direct-current magnetic sensor with a wide dynamic range from milliamp level to hundred-ampere level, which is characterized in that a first induction circuit, a second induction circuit, a power frequency current conditioning circuit and a weak current conditioning circuit are arranged, the first induction circuit and the power frequency current conditioning circuit adopt a tunneling magneto-resistance technology and a magnetic balance principle to induce a wide-frequency mixed current to be detected and extract the power frequency current in the wide-frequency mixed current to be detected to obtain a power frequency feedback current, the second induction circuit adopts the magnetic balance principle to induce the wide-frequency mixed current to be detected, the power frequency feedback current is received to offset the power frequency part in the wide-frequency mixed current to be detected, the tunneling magneto-resistance technology is adopted to induce the residual weak current after the power frequency part is offset, and the weak current conditioning circuit is used for measuring the weak current. The power frequency part in the broadband mixed current to be detected is counteracted by extracting and inputting the power frequency current to the second induction circuit, so that the problems that the second induction circuit is saturated and cannot perform weak current measurement when the second induction circuit performs current measurement by adopting a tunneling magnetic resistance technology are avoided, and meanwhile, the power frequency current and the weak current are measured by the first induction circuit, the second induction circuit, the power frequency current conditioning circuit and the weak current conditioning circuit. The method solves the problem that the measurement of weak current in broadband mixed current is difficult to realize by adopting a traditional current transformer in the related technology.
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected, mechanically connected, electrically connected, directly connected, indirectly connected via an intermediate medium, and in communication with each other between two elements, and wirelessly connected, or wired. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
The embodiment of the invention provides a wide-frequency alternating-current/direct-current magneto-sensor with a large dynamic range from milliamp level to hundred-ampere level, which is shown in fig. 1, and comprises a first induction circuit 10, a second induction circuit 20, a power frequency current conditioning circuit 40 and a weak current conditioning circuit 30, wherein the first induction circuit 10 and the second induction circuit 20 are respectively connected with the power frequency current conditioning circuit 40, the second induction circuit 20 is connected with the weak current conditioning circuit 30, the first induction circuit 10 and the power frequency current conditioning circuit 40 adopt a tunneling magneto-resistance technology and a magnetic balance principle to induce a broadband mixed current to be detected and extract a power frequency current in the broadband mixed current to be detected, a power frequency feedback current is obtained and is input into the second induction circuit 20, the second induction circuit 20 adopts the magnetic balance principle to induce the broadband mixed current to be detected, the power frequency feedback current is received to offset a power frequency part in the broadband mixed current to be detected, the tunneling magneto-resistance technology is adopted to induce the residual weak current after the power frequency part is offset, and the weak current conditioning circuit 30 carries out weak current measurement. The power frequency feedback current input into the second induction circuit is the power frequency current in the broadband mixed current to be detected, which is extracted by the power frequency current conditioning circuit, and the power frequency current is input into the second induction circuit to realize the negative feedback function, so that the power frequency current input into the second induction circuit is called as the power frequency feedback current.
The wide-frequency alternating-current and direct-current magneto-sensor with the wide dynamic range from milliampere level to hundred ampere level provided by the embodiment of the invention adopts the tunneling magneto-resistance technology to induce the wide-frequency mixed current to be measured, fully exerts the advantages of high sensitivity, low power consumption, simple structure, non-invasiveness and the like of the tunneling magneto-resistance current measurement technology, and simultaneously adopts the magnetic balance principle to realize the measurement of the wide-frequency mixed current to be measured and the extraction of the power frequency current by combining the first induction circuit with the power frequency current conditioning circuit, inputs the power frequency current into the second induction circuit, and partially counteracts the power frequency in the wide-frequency mixed current to be measured induced by the second induction circuit, thereby avoiding the problems that the second induction circuit is saturated and cannot perform weak current measurement due to the fact that the power frequency current is large.
In one embodiment, as shown in fig. 2 and 3, the first sensing circuit 10 includes a first magnetic core 11 provided with an air gap, a first feedback coil 12, and a high saturation magnetic resistance chip, wherein the first feedback coil 12 is wound on the first magnetic core 11, the high saturation magnetic resistance chip is disposed in the air gap, and the high saturation magnetic resistance chip senses a broadband mixed current to be measured by using a tunneling magnetic resistance technology. The second induction circuit 20 comprises a second magnetic core 21 provided with an air gap, a second feedback coil 22 and a high-sensitivity magnetic resistance chip, wherein the second feedback coil 22 is wound on the first magnetic core 11, the high-sensitivity magnetic resistance chip is arranged in the air gap, and the high-sensitivity magnetic resistance chip adopts a tunneling magnetic resistance technology to induct weak current remained after the power frequency part is counteracted.
Specifically, as shown in fig. 2, in order to facilitate the first induction circuit and the second induction circuit to induce the broadband mixed current to be measured, the first magnetic core and the second magnetic core may be sleeved outside the conductor to be measured, such as a copper bar, so that the conductor to be measured passes through the inner holes of the first magnetic core and the second magnetic core, and simultaneously the first feedback coil and the second feedback coil are wound around the two magnetic cores, the high-saturation reluctance chip and the high-sensitivity reluctance chip are respectively arranged in the air gaps of the corresponding magnetic cores, and when the broadband mixed current to be measured passes through the conductor to be measured, the first feedback coil and the second feedback coil wound around the first magnetic core and the second magnetic core respectively form a secondary coil corresponding to the conductor to be measured, thereby realizing the induction of the broadband mixed current to be measured in the conductor to be measured.
When current flows in the conductor to be tested, the two magnetic cores can gather the induction magnetic field generated by the conductor to be tested in space, and the magnetic field in the air gap is stronger, so that the chip is placed in the air gap to easily realize the induction of the current. The sensitivity of the high-saturation magnetic resistance chip is lower than that of the high-sensitivity magnetic resistance chip, but the high-saturation magnetic resistance chip is not easy to saturate when the current is large, so that the high-saturation magnetic resistance chip is adopted to induce large current, namely power frequency current, and the high-sensitivity magnetic resistance chip is adopted to induce small current, namely weak current.
In an embodiment, as shown in fig. 4, the power frequency current conditioning circuit 40 includes a compensation circuit 41, a sampling resistor RB, a current mirror circuit 42 and a band-pass filter 43, wherein one end of the compensation circuit 41 is connected to the high saturation reluctance chip, the other end of the compensation circuit 41 is connected to one end of the first feedback coil 12, the other end of the first feedback coil 12 is connected to one end of the current mirror circuit 42 through the sampling resistor RB, the compensation circuit 41 is used for recording the broadband mixed current to be detected induced by the high saturation reluctance chip, the other end of the current mirror circuit 42 is connected to one end of the band-pass filter 43, the other end of the band-pass filter 43 is connected to the second feedback coil 22, the current mirror circuit 42 is used for copying and outputting the broadband mixed current to be detected recorded by the compensation circuit 41, and the band-pass filter 43 is used for extracting the power frequency current in the broadband mixed current to be detected outputted by the current mirror circuit 42 to obtain the power frequency feedback current, and inputting the power frequency feedback current to the second feedback coil 22.
Specifically, as shown in fig. 4, the compensation circuit includes an amplifying circuit, an integrating circuit, a filter circuit, and a push-pull output circuit, which are sequentially connected. The amplifying circuit mainly comprises a first operational amplifier U1, the integrating circuit mainly comprises a second operational amplifier U2, the filtering circuit mainly comprises a third operational amplifier U3, the push-pull output circuit comprises a third triode Q3, a fourth triode Q4, a first diode D1 and a second diode D2, and meanwhile, the compensating circuit also comprises other resistors, capacitors and the like, and the corresponding functions are realized together with main components. Meanwhile, in fig. 4, the first feedback coil 12 is equivalent to a tenth resistor R10, an eleventh resistor R11, a first inductor AM1, and a second inductor AM2, and the second feedback coil is equivalent to a twelfth resistor R12 and a third inductor L1. In fig. 4, I represents a broadband mixed current to be measured flowing through a conductor to be measured, n1 represents a primary coil, and n2 represents a secondary coil.
As shown in FIG. 4, the current mirror circuit comprises a first resistor R1, a first triode Q1 and a second triode Q2, wherein one end of the first resistor R1 is connected with the other end of the compensation circuit, the other end of the first resistor R1 is connected with a collector electrode and a base electrode of the first triode Q1 and a base electrode of the second triode Q2, an emitter electrode of the first triode Q1 is connected with an emitter electrode of the second triode Q2 and grounded, and a collector electrode of the second triode Q2 is connected with one end of the band-pass filter. The band-pass filter comprises a first capacitor C1, a second capacitor C2 and a second resistor R2, wherein one end of the first capacitor C1 is connected with the other end of the current mirror circuit and one end of the second resistor R2, the other end of the second resistor R2 is connected with one end of the second capacitor C2, and the other end of the first capacitor C1 is connected with the other end of the second capacitor C2 and grounded.
Specifically, by arranging the amplifying circuit, the integrating circuit, the filtering circuit and the push-pull output circuit in the compensating circuit, the amplifying circuit and the integrating circuit form a proportional integrator, the compensating circuit is connected with the high-saturation magnetic resistance chip, the proportional integrator can record the current output and the historical output of the high-saturation magnetic resistance chip, and the output of the high-saturation magnetic resistance chip is in direct proportion to the error of the primary side current and the secondary side current passing through the first magnetic core, namely the proportional integrator records the error of the primary side current and the secondary side current. The output of the compensation circuit is connected to one end of a first feedback coil, and the other end of the first feedback coil is connected to a sampling resistor of the power frequency current conditioning circuit. As shown in fig. 3 and 4, the output of the compensation circuit is the main output. The output of the current mirror circuit is a secondary output terminal.
In one embodiment, as shown in FIG. 5, the weak current conditioning circuit includes an amplification filter circuit and a trap. The amplifying and filtering circuit mainly comprises a fourth operational amplifier U4 and a thirteenth resistor R13, and the trap comprises a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a fourth capacitor C4, a fifth capacitor C5 and a sixth capacitor C6. As shown in FIG. 3, the milliamp-level to hundred-amp-level wide dynamic range broadband AC/DC magneto-sensor further comprises a power supply, wherein the power supply is used for supplying power to the first induction circuit, the second induction circuit, the power frequency current conditioning circuit and the weak current conditioning circuit. The power supply is powered by adopting a mode of externally inputting electric energy, photovoltaic energy storage or magnetic field energy taking.
As shown in fig. 6 and fig. 7 (n=1/59.4x1e-2 in fig. 7), the measurement principle of the milliamp-level to hundred-level wide dynamic range broadband ac/dc magneto-sensor is described:
When the broadband mixed current to be measured flows through the conductor to be measured, the primary side current I1 (broadband mixed current to be measured), the exciting current Im and the secondary side current I2 form a balance relation for the first induction circuit according to the magnetic potential balance principle of the current transformer.
Wherein n1 is the number of turns of the primary winding, and n1 is equal to 1 when the conductor to be tested is a single wire or copper bar structure. n2 is the number of secondary winding turns, i.e., the number of first feedback coil turns.
For the first core, the excitation current generates a magnetic potential in the air gap, which has a switching relationship,
Where mu0 is the vacuum permeability, Ac is the core air gap area, lg is the air gap length, in FIG. 6,
A part of the excitation magnetic potential is converted into the excitation potential of the secondary winding, as shown in the following formula:
Wherein Lm is excitation inductance, V2 is excitation potential, and the corresponding expression in Laplace domain is shown as follows:
V2＝sLmIm
Where s represents the Laplace domain complex frequency.
Meanwhile, the excitation magnetic potential excites a high-saturation magnetic resistance chip arranged in an air gap to generate output, the output is recorded as VAmp after passing through a compensation circuit, the output and the excitation potential are overlapped on a series circuit formed by a first feedback coil and a sampling resistor RB together, and at the moment, the current flowing through the first feedback coil is shown by the following formula:
Where r2 represents the equivalent resistance of the first feedback coil.
At this time, the output of the sampling resistor is:
If the high saturation magnetoresistive chip is operating in the linear region at all times, VAmp can be represented as.
Where Kh is the sensitivity of the high saturation magnetoresistive chip and Gc(s) is the transfer function of the compensation circuit.
When the magnetic balance system formed by the first induction circuit and the power frequency current conditioning circuit enters a magnetic balance state, the expression of V2、VAmp、I2、I1 and Im is brought into the following magnetic potential balance equation,
From the above formula, if the transfer function Gc(s) of the compensation circuit is designed reasonably so that H(s) is sufficiently large and remains stable, the magnetic balance system can enter a locked state, that is, the secondary side current I2 locks the primary side current, and according to the output expression of the sampling resistor, the output of Vout1 is directly proportional to the primary side current, and the primary side current, that is, the power frequency current in the broadband mixed current to be detected, can be extracted through the band-pass filter.
Meanwhile, after the secondary side current I2 is copied by the current mirror circuit, the power frequency part is input into a second feedback coil of a second magnetic core through a band-pass filter, and for a second induction circuit, according to the magnetic potential balance principle, the primary side current I '1, the exciting current I 'm and the secondary side current I '2 form a balance relation:
As described in the above equation, the secondary current I'2 of the second feedback coil on the second core is the power frequency portion of the secondary current I2 of the first feedback coil on the first core due to the action of the current mirror circuit and the band pass filter. Therefore, the power frequency part of the exciting magnetic potential of the second magnetic core is counteracted to prevent the high-sensitivity magnetic resistance chip from saturation, and at the moment, the exciting current I 'm only contains the frequency of weak characteristic current, and the high-sensitivity magnetic resistance chip generates a corresponding voltage signal under the excitation of the exciting current I'm and is sampled by the weak current conditioning circuit.
Fig. 8 (a) and 8 (b) are schematic calculation results according to the Simulink model established in fig. 6, and waveform changes caused by the large amplitude current of the power frequency and weak currents such as direct current, harmonic waves and inter-harmonic waves can be clearly seen through waveforms. Before the first period is 0.2s, the first induction circuit and the power frequency current conditioning circuit do not enter a magnetic balance state, the secondary side current is not locked with the primary side current, the feedback magnetic potential in the second magnetic core does not completely counteract the power frequency magnetic potential in the primary side current, and the output waveform is in oscillation. After the secondary side feedback current locks the primary side current after 0.2s, the power frequency feedback magnetic potential in the primary side current is counteracted by the power frequency magnetic potential in the second magnetic core, and the high-sensitivity magnetic resistance chip is only influenced by the high-frequency magnetic potential and outputs a voltage waveform with corresponding frequency.
According to the embodiment of the invention, the power frequency current is injected into the second feedback coil to counteract the induction magnetic field generated by the large-amplitude power frequency current, so that the saturation of the high-sensitivity tunneling magneto-resistance chip is avoided. Taking the ground fault finding scene of the overhead line active injection method as an example, assuming that the rated current of the line is 600A and the rated load of the line is 50% in normal times, the current injected by the high-frequency method is coupled to the line through the grounding point, wherein the amplitude value is 0.1A and 800Hz, and the magnitude of the induction magnetic field generated by the current with the amplitude value of 300A at the frequency of 50Hz and the current with the amplitude value of 0.1A at the frequency of 800Hz is compared with that shown in fig. 9 (a) and 9 (b). It can be seen that the induced magnetic field generated by the 50Hz current is about 70mT, and the induced magnetic field generated by the 800Hz current is about 20 μt, so that in order to realize the measurement of the high-frequency weak current, the equivalent magnetic noise of the tunneling magneto-resistance device needs to be at nT level, and the magnetic saturation strength of the high-sensitivity tunneling magneto-resistance device with low noise is usually not more than 1mT, so that if the power frequency magnetic field is not counteracted, the high-sensitivity tunneling magneto-resistance device is always in saturated state, and the magnetic field generated by the weak current cannot be accurately measured. By adopting the method provided by the invention, the simultaneous measurement of 600A power frequency current, mA level direct current, harmonic wave and inter-harmonic wave can be realized, and the measurement precision can be controlled to be 0.2% -1% by adopting the existing commercial tunneling magnetic resistance sensing chip.
The milliamp-level to hundred-amp-level wide-dynamic-range broadband alternating current-direct current magneto-dependent sensor provided by the embodiment of the invention is provided with the high-saturation magneto-resistance chip and the high-sensitivity magneto-resistance chip, wherein the high-saturation magneto-resistance chip is used for measuring the power frequency current with large amplitude, and meanwhile, the power frequency current is injected into the second feedback coil to counteract the induction magnetic field generated by the power frequency current with large amplitude, so that the saturation of the high-sensitivity tunneling magneto-resistance chip is avoided. Therefore, the high-sensitivity tunneling magneto-resistance chip can work normally, can measure weak direct current, harmonic and inter-harmonic components superposed on large-amplitude power frequency current, and can be applied to the scenes such as high-precision harmonic and direct current magnetic bias current monitoring of a distributed power supply access scene, line single-phase grounding fault searching based on a high-frequency injection method and the like.
Although the exemplary embodiments and their advantages have been described in detail, those skilled in the art may make various changes, substitutions and alterations to these embodiments without departing from the spirit of the invention and the scope of protection as defined by the appended claims. For other examples, one of ordinary skill in the art will readily appreciate that the order of the process steps may be varied while remaining within the scope of the present invention.
Furthermore, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. From the present disclosure, it will be readily understood by those of ordinary skill in the art that processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.